Monitoring of PON System Using Compound Surveillance Technique

A passive optical network (PON) monitoring system combined light pulse and frequency sweep techniques is proposed and verified in a field test. The light pulse surveys over the all whole network and th...     

Effective identification of dominant fully absorbing sets for Raptor-like LDPC codes

The error-rate floor of low-density parity-check (LDPC) codes is attributed to the trapping sets of their Tanner graphs. Among them, fully absorbing sets dominantly affect the error-rate performance, especially for short blocklengths. Efficient methods to identify the dominant trapping sets of LDPC codes were thoroughly researched as exhaustively searching them is NP-hard. However, the existing methods are ineffective for Raptor-like LDPC codes, which have many types of trapping sets. An effective method to identify dominant fully absorbing sets of Raptor-like LDPC codes is proposed. The search space of the proposed algorithm is optimized into the Tanner subgraphs of the codes to afford time-efficiency and search-effectiveness. For 5G New Radio (NR) base graph (BG) 2 LDPC codes for short blocklengths, the proposed algorithm finds more dominant fully absorbing sets within one seventh of the computation time of the existing search algorithm, and its search-effectiveness is verified using importance sampling. The proposed method is also applied to 5G NR BG1 LDPC code and Advanced Television Systems Committee 3.0 type A LDPC code for large blocklengths.     

Defect Analysis of Ionically Compensated Quadruple and Quintuple Perovskite Layered Cuprates with Ti Blocking Layers

This work presents a modified defect model for pure and chemically substituted quadruple and quintuple pure perovskite layered cuprates, using data from the Jonker (thermopower vs ln conductivity) and Brouwer (log conductivity vs log pO₂) analyses. The closely matched in-plane bond lengths of the blocking and the active layers in these structures promote ionic compensation rather than electronic compensation upon aliovalent p-type doping. A comprehensive defect model that takes into account all the major defect species in an ionically compensated quadruple or quintuple perovskite provides a better means for understanding the electrical behavior of these novel materials. The presented model allows for the calculation of effective dopant and the oxygen interstitial concentrations in these materials.     

Scattering from a Periodic Array of Double-Dipole Elements over a Grounded Dielectric Slab

An analysis method of electromagnetic scattering from periodic patch array of double-dipole elements on a grounded dielectric substrate in case of oblique incident and arbitrary polarization is considered. The basis functions are chosen to be entire cosinusoidal functions covering the rectangular shaped domain in which the original dipoles are inscribed, unlike the conventional method in which basis functions are defined only for the conducting element region. To confirm the validity of the proposed analysis method, we calculate the normalized scattered power for two propagating modes and compare the results with those obtained by the previous numerical method for the double dipole elements of rectangular type and parallelogram type which have the property of frequency scanned reflection and polarizer. Good correspondence has been observed between them. Some numerical results such as variation of power and axial ratio of first-order diffracted wave by a periodic array of double-dipole elements are compared with previous results.     

Dynamic aspects of phase decomposition in reactive blends of polycarbonate and syndiotactic polymethyl methacrylate

Dynamics of phase separation in bisphenol-A polycarbonate (PC)/syndiotactic polymethyl methacrylate (sPMMA) blends has been investigated by means of time-resolved light scattering. Solvent-cast films of the PC/sPMMA blends were transparent, suggestive of miscible character. Several temperature jumps were carried out at a 50/50 PC/sPMMA composition from a homogeneous state (room temperature) into a two-phase regime. The process of phase separation first occurred for some considerable period, then it was followed by phase dissolution driven by chemical reaction. The thermodegradative reaction of sPMMA triggered the dissolution process by probably forming PC/sPMMA graft or random copolymers at the interface, which eventually resulted in a single phase. However, annealing at elevated temperatures for an extended period could lead to cross-linking, and thus a two-phase structure could be fixed permanently. The early stage of spinodal decomposition was interpreted in terms of the linearized Cahn-Hilliard theory. In the late stages of spinodal decomposition, the relationship between scattering peak wavenumber and time was found to obey a power law, but the exponents showed a strong dependence on temperature jumps. The temporal universal scaling failed due to the influence of the chemical reaction. © 1995 John Wiley & Sons, Inc.     

A new device for in-situ movement detection and measurement

A new device for movement detection in joints is designed using the moiré technique. Archimedean spiral grids are used. A space displacement may be evaluated in two planes by vectors of known magnitudes and directions. An extremely simple design is proposed to provide stability for the system being installedin situ over long periods of time.     

A one-dimensional statistical model of friction in deeply inelastic heavy ion collisions

We use the semiclassical approximation for the relative motion (which is simplified and taken to be one-dimensional), neglect other collective degrees of freedom, and describe the coupling between relative motion and intrinsic degrees of freedom by a random-matrix model. This leads to an explicit expression for the friction coefficient. Numerical calculations show qualitative agreement with the data.     

Coherent structures in subsonic coaxial jets

This paper describes a detailed study of the initial region of coaxial jets and the large scale coherent structures within this region. The coaxial jets investigated have an area ratio of 2·67 and were run at three different velocity ratios. A simple model in terms of two arrays of vortex-rings in the mixing region of the coaxial jet is proposed, and its use verified by comparisons with experimental results. Overall and spectral results of hot wire and microphone signals, obtained in the flow, support the model proposed. Evidence supporting the concept of a preferred mode, which governs the growth or decay of the vortices in the intermediate zone, is also presented.